People can be exposed to pressure waves. For example, military, law enforcement, and construction personnel can be exposed to explosions, blasts, or similar events when performing their duties. Medical experts are looking to correlate long-term injury with recordable blast signatures.
Monitoring devices may be segregated into two classes: (1) those that detect the peak level of a pressure wave, and (2) those that record the entire pressure waveform.
Monitoring devices that monitor only the peak level (e.g., the first class described above) fail to provide a rich dataset needed for research and injury tracking purposes.
Monitoring devices that record the entire pressure waveform (e.g., the second class described above) are subject to poor battery life due to the power requirements associated with the data acquisition components included in such devices. The nature of blasts and similar events is that they tend to be unpredictable in terms of when they will occur. An example of such a circuit 300 is shown in FIG. 3A.
The circuit 300 includes a sensor 1. The circuit 300 includes a conditioning amplifier 2 coupled to the sensor 1.
The output of the conditioning amplifier 2 is coupled to a first input associated with each of a number ‘n’ of comparators 4, denoted in FIG. 3A as 4_1, 4_2, 4_3, . . . 4_n. A second input of the comparators 4 is supplied with a reference voltage 7. Specifically, a reference applied to the comparators 4 corresponds to the reference voltage 7 divided by a resistor divider network composed of a number ‘n’ of resistors 3, denoted in FIG. 3A as resistors 3_1, 3_2, 3_3, . . . 3_n, 3_n+1. The outputs of the comparators 4 are provided to a network of latches composed of a number ‘n’ of latches 5, denoted in FIG. 3A as latches 5_1, 5_2, 5_3, . . . 5_n. The state of each of the latches 5 is reset by a reset signal 8. The output of each of the latches 5 is coupled to a network of indicators composed of a number ‘n’ of indicators 6, denoted in FIG. 3A as indicators 6_1, 6_2, 6_3, . . . 6_n. The indicators 6 include light emitting diodes (LEDs).
The comparators 4 and latches 5 record only the maximum magnitude of an input wave. They record the time of occurrence of the blast event, but do not have the capability of recording the time characteristics (e.g., blast waveform).